1. Field of the Invention
The present invention in general relates to a scroll type compressor, and in particular, to a scroll type compressor used, for example, in an air conditioning system of a vehicle.
2. Description of the Related Art
Generally speaking, a conventional scroll type compressor comprises a fixed and a movable spiral element mounted on respective base plates and disposed inside a compressor housing. Contacting sidewall portions of scroll elements form compression chambers between the spiral elements in which refrigerant gas is compressed. During the compressor's operation, an eccentric shaft coupled to a rotary shaft causes the movable scroll to orbit in a circular locus, while anti-rotation devices prevent the movable scroll from rotating around its own axis. A suction chamber, defined between the inner wall of the housing and the spiral elements, supplies refrigerant gas to the compression chambers. As each compression chamber moves toward the inner tip portions of the spiral elements from the outer tip portions, the volume of the compression chamber decreases, compressing the refrigerant gas inside the compression chamber. The compressed refrigerant gas is then discharged into a discharge chamber in the housing via a discharge port formed in the center portion of the end plate of the fixed scroll.
Japanese Unexamined Utility Model Publication No. 4-91294 discloses a conventional scroll type compressor. This compressor, as illustrated in FIG. 10, uses a balance weight 50, attached to an eccentric shaft 52 and disposed in a crank chamber 53, to counter the dynamically unbalanced rotation of the movable scroll 51. This design prevents abnormal levels of compressor vibration.
A bushing 54, movably fitted in a boss 55 via a radial bearing 56, fits onto the eccentric shaft 52. The boss 55 is formed on the end plate of the movable scroll 51. A narrow gap 57, between the inner wall of the boss 55 and the bushing 54 communicates with the crank chamber 53 via a passage 58 formed in the bushing 54 and the balance weight 50.
A suction port (not shown), provided in the center portion of the outer surface of the compressor housing, supplies refrigerant gas from a circuit outside the compressor to the suction chamber formed between the housing and the movable scroll 51. The crank chamber communicates with the suction chamber via a gap formed in the anti-rotation devices.
Consequently, the supply of lubricating oil to the radial bearing 56, according to conventional compressor design, must pass from the suction port to the suction chamber and crank chamber. This requirement reduces the amount of lubricating oil supplied to the radial bearing 56, and effectively limits the serviceability and durability of the bearing 56 as well as that of the compressor.
Much the same is true with respect to yet another bearing, located proximate to the crank chamber between the rotary shaft and compressor housing. This rotary bearing supports the rotary shaft at the location where the rotary shaft extends to the exterior of the compressor. A seal, provided between the rotary bearing and exterior, prevents refrigerant gas and oil leakage from the crank chamber to the exterior of the compressor. Inherent to the rotary bearing's design is a gap which extends through the bearing, to the rotary shaft via a clearance between the rotary bearing and seal. This gap allows oil to be supplied from the crank chamber to the rotary shaft and seal in order to prevent premature wearing of the seal.
As in the case of the radial bearing 56, the rotary shaft bearing receives a supply of lubricating oil that must pass from the suction port to the suction chamber and crank chamber. This requirement effectively reduces the amount of oil supplied not only to the radial bearing, but also to the rotary shaft and seal. This limits the serviceability and durability of the seal, rotary bearing and the compressor.